Reversible propeller blade



Sept, 2, 1952 J H. K. MONROE v 2,609,055

I REVERSIBLE PROPELLER BLADE Filed Nov. 8, 1949 v 2 mars-4mm 1 mnscmu 0F nonmon g 3 rn scnon-or A m now INVENTOR ByOMER K.-MONROE-' "1mm 8' WW ATTORNEYS Sept. 2, 1-952 H. K. MONROE REVERSIBLE PROPELLER BLADE Filed NOV. 8, 1949 INVENTOR- W W N 7% o E M K n R A E Patented Sept. 2, 1952 REVERSIBLE PROPELLER mans Homer K. Monroe, Fiqna, Ohio, assignorto Hartw zell Propeller Fan Company, Fiqumbhima corporation of Ohio Application November 8, 194.9, Serial No. 126,162

This invention relates to fans or propellers adapted for reversible operation for selectively moving a gas, such as air, in one direction or the other.

A number of circumstances are encountered in industry where it is desired to move air first in one direction and then inanother, as, for ex ample, in connection with the operation of kilns and the like. Heretofore it has not been possible to obtain a ianfor this purpose which is eflicient in moving the air in both directions, and as a result the use of such fans has entailed a considerable loss of power and efficiency.

The particular object of the present invention is the provision of an fan or propeller having blades so constructed that the fan will have substantially equal aerodynamic qualities in either direction of rotation.

A further object is the design of a reversible propeller which is relatively efiicient in either direction of rotation and which can therefore be operated in either direction without any substantial loss of power.

These and other objects and advantages will become more apparent upon reference to the following description taken in connection with the accompanying drawings in which:

Figure l is a sectional view showing a propeller or fan according to my invention mounted in a duct for moving air reversibly therethrough;

Figure 2 is an end view of .the arrangement of Figure 1;

Figure 3 is a diagrammatic view of a section through one bladeof the propeller fan, as indicated by line 3'-3 on Figure 2;'Figure 3 shows the pressure conditions which exist on the propeller blade for one directionoi rotation thereof Figure 4 is similar to Figure 3 but shows the pressure conditions which obtainon the reverse direction or rotation;

Figure 5 is a front elevational view of one blade of the propeller drawn at a scale considerably greater than is employed in Figures 1 and 2;

Figure 6 is a, view of theblade looking in from the side of Figure 5; and

Figures 7 through 12 are sectional views indicated by the lines 'l-l through l2-I2, respectively, on Figure 5. I

Referring to the drawings somewhat more in detail, the propeller or fan according to my invention is generally indicated at I0 and comprises the radially extending blade parts 12 which are mounted on a hub I4 adapted for being secured to a driving element such as shaft It. In the drawings, shaft 16 is the output shaft of a re- 3 Claims. (01, -159) versible motor I8, but it will be understood that shaft It could be driven by aflexible drive shaft, by belts, or by other means, if so desired.

Surrounding theipropeller or fan is a duct 26 having tapered inlet and outlet portions 22 and 24. The particular configuration which the duct takes is more fully set forth and explained in the co-pending application Serial No. 126,168, filed November 8, 1949, in the names of Donald D. Herrman and H. K. Monroe and assigned to the same assignee as the instant application.

According to, the present invention, the propeller i0 is adapted for moving air through duct 26 in either direction, depending on the direction of rotation which is given the propeller;- It is desired for the propeller to be efficient inrboth directions of rotation thereof, and to accomplish this I have devisedthe blade construction which is illustrated in detail in Figures 5 through 12. This blade construction is characterized by being, in fact, two air foils placed together back-to-back and in reverse order, so as to form a section which is symmetrical about a radial axis through the blade. It has been found by extensive tests and experimentation that an. air foil section of this nature exhibits substantially equal efiiciency in either direction of movement, and by further test and experiment, the particular blade configuration illustrated in this application has been found highly eiiicient in both directions of movement.

Referring to Figures 5 through 12, it will be seen that the blade l2 illustrated therein consists of arather elongated central part 25 oi a predetermined width with the opposite ends of the blade tapering inwardly somewhat, as indicated at 28, adjacent the hub of the blade and at 30, adjacent the tips of the blade.

As will be seen from the sectional views Figures 7 through 12, the thickness of the blade measured substantially normally to a plane passing through the edges of the blade diminishes more or less uniformly toward the blade tip.

The configuration'of the blade in section at substantially any point therealong consists of a substantially wholly convex shape terminating in edge partswhich are either leading or trailing, depending on the direction of movement of the propeller blade. This can be brought out by considering Figure 12. In Figure 12, the blade edge, indicated at 32, is leading when the blade is moving in adirection toward the said edge, while the edge 34 is leading when the blade is moving in the opposite direction.

Relative to the edge 32, the upper portion of Figure 12 is the leading face of the blade, whereas the bottom face is leading relative to the edge 34. Each of the said faces consists of a substantially flat portion 36 extending from the leading edge corresponding to that face toward the mid-point of the blade. The other part of the face of the blade comprises an arcuate portion, indicated at 38, extending from the end of the aforementioned substantially straight portion to the trailing edge of the blade pertaining to that face.

It has been stated that the portion 36 of each face is substantially flat, and this is in effect true, although each portion 36 is slightly convex. Because of this, each face of the propeller blade is characterized by decreasing in curvature from the trailing edge pertaining to that face to the leading edge. The edges of the blade are, of course, filleted in order smoothly to join the opposite faces of the blade.

I have also found it to be of considerable advantage to vary the blade angle from the hub end to the tip end of the blade. The various blade angles of the several sections along the blade are illustrated'i'n Figures 7 through 12, and it Will be seen that the innermost section of the blade, Figure 12', has an angle of 38 degrees, whereas the outermost section has an angle of 16 degrees.

It will be understood that the particular blade angles are subject to variation depending on the nature of the duct in which the blade runs, the quality of the gas being moved, and the speed of rotation of the propeller blade, and that the particular angles illustrated in Figures 7 through 12 are merely exemplary of one highly efi'icient arrangement which I have arrived at in connection with a propeller that is to run about eighteen hundred revolutions per minute for moving air.

In any case, the propeller blade is characterized by being twisted from its hub end toward its tip end, so as to decrease the blade angle, and each section through the blade is of substantially identical shape and is symmetrical about a radial axis through the blade.

As representative of the improved results which have been obtained by a reversible propeller having blades according to this invention, Figures 3 and 4 may be referred to for the pressure conditions which exist on the-opposite faces of the blades for opposite directions of rotation.

In Figure 3 the direction of movement of the blade is toward the left and the direction of air flow is downward. The pressure acting on the blade is represented by the arrows 40 standing out from the back face of the blade and the arrows 42 which are exerted against the front face of the blade. The arrows 40, of course, represent a suction, whereas the arrows 42 represent positive pressure, but, as is well known, both of these pressures contribute to the movement of air through the fan.

The distribution of pressure over the face of the blade, as represented in Figure 3, indicates that the blade is relatively efiicient in operation, and that there areno serious power consuming losses due to vortexes and agitation of air.

Figure 4 illustrates the conditions which obtain when the blade is moving rightwardly in the opposite direction to the direction of movement in Figure 3. In Figure 4 it will be evident that the same conditions obtain as in Figure 3, except that the location of the pressure and suction arrows 40 and 42 is reversed.

From the foregoing, it will be evident that I have invented a propeller having a number of distinct advantages, among which are:

(a) Air is reversibly moved merely by reversing the direction of rotation of the propeller by using a reversible motor or a reversing clutch means, or the like, and thus expensive constructions utilizing pitch changing mechanisms are entirely avoided.

(b) The propeller blade has substantially equal efliciency in both directions of rotation, thereby preventing the customary loss of power when operating in the reverse direction. (c) The particular blade form which I have invented has relatively high emciency, thereby leading to eflicient operation of the propeller in either direction of rotation.

It will be understood that this invention is susceptible to'modification in order to adapt it to different usages and conditions, and, accordingly, it is desired to comprehend such modifications within this invention as may fall Within the scope of the appended claims.

I claim:

1. A reversible propeller comprising a hub, at least one blade extending outwardly therefrom, said blade having leading and trailing edges and being twisted about a central radial axis so as to decrease in blade angle toward the tip end, said blade being made up of integral sections which are symmetrical about said central axis, each of said sections comprising outer surfaces which are convexly curved throughout their length, said blade sections being asymmetrical with respect to the chord which divides said blade into said sections, and the edges of the blade formed of said sections being rounded to provide a smooth continuous surface.

2. A reversible propeller comprising a hub, at least one blade extending outwardly therefrom, said blade having leading and trailing edges and being twisted about a central radial axis so as to decrease in blade angle toward the tip end, said blade being made up of integral sections which are symmetrical about said central axis, each of said sections comprising outer surfaces which are convexly curved throughout their length, said blade sections bein asymmetrical with respect to the chord which divides said blade into said sections, the edges of the blade formed of said sections being rounded to provide a smooth continuous surface, and said blade having a thickness diminishing uniformly from the hub end to the tip end.

3. A reversible propeller blade according to claim 1 in which the angle of the blade adjacent the hub is approximately 38 degrees and adjacent the tip is approximately 16 degrees.

HOMER K. MONROE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 342,011 Hoehle May 18, 1886 652,123 Lavigne June 19, 1900 1,082,750 Jacomy Dec. 30,1913 2,027,647 Montgomery Jan. 14, 1936 FOREIGN PATENTS Number I Country Date 296,717 Great Britain Sept. 3, 1928 

